In rotor machines, such as, for example, labeling, expansion blowing, inspection and closing machines for containers, such as bottles, cans, beakers or similar items; during the filling of such containers; in cleaning machines, for example rinsing machines, for such containers and similar items, the position of a rotor has to be determined with high precision.
Such rotor machines as a rule present a multitude of similar devices that are arranged in a certain angular distribution over the circumference of the rotor.
Thus, a labeling machine can have, for example, up to 60 or 70 rotating plates or more, by means of which containers to be labeled can be positioned to allow the correct positioning of the labels on the containers.
In the case of filling machines, it is possible to distribute a similar number of filling valves over the circumference of the rotor.
The angular distance between two such identical installations is called the machine partition.
To be able to achieve, during the treatment of the objects with the rotor machine, as precise as possible a control, it is necessary to know the position of the rotor with respect to the machine partition. This means that, in the case of a machine with a machine partition of, for example, 10°, this angular range has to be known precisely with a resolution of 1/500°.
Depending on the requirements, smaller or higher resolutions can also be possible.
From the applicable state of the art, it is known, for example, from DE 694 11 178 T2, to provide a sensor-toothed wheel on one of the driving wheels of the shaft of the rotor, which wheel is connected to the rotary encoder.
It is known from practice here to adjust the sensor-toothed wheel and the driving toothed wheel in such a manner that the rotation of the rotor by one machine partition corresponds to turning rotary encoder by one rotation. Thus, if a rotor with a machine partition of 10° is rotated by 10°, then the sensor-toothed wheel has turned once by 360°. The rotary encoder can generate signals that reflect its position in the case of a full rotation at a desired resolution.
The drawback here is that a special sensor-toothed wheel must be constructed for each machine partition, so that the rotation of the rotor by one machine partition corresponds to a full rotation of the sensor-toothed wheel.